This invention relates generally to systems and methods for inspecting manufactured articles and more particularly to systems and methods for locating hole features on a manufactured article.
In gas turbine engines, fuel is combusted in compressed air in order to accelerate high-density air and to produce thrust, which, in turn, are used to turn a turbine shaft and drive an aircraft, respectively. During the combustion process, the air is heated to super-high temperatures in order to accelerate the air to produce the thrust. Thus, blades of the turbine, which are downstream of the combustion process, are also subject to super-high temperatures. In order to facilitate cooling of the blades, many turbine blades incorporate complex systems of internal cooling passages into which compressor bleed air, or another cooling fluid, is directed to cool the blade. The cooling air exits the blade through a system of holes arranged in such a manner that the exterior surface of the blade is cooled, and is then passed out of the engine with the rest of the exhausted gases.
In some turbine blade embodiments, the exit holes are arranged in a specific pattern on various facets of the blade to create a surface cooling film. The surface cooling film creates a layer of cool air, which insulates the airfoil from the hot gases of the combustion process. In order to ensure that the surface cooling film properly forms, various shaped exit holes are precisely located and bored at various angles on the surface of the blade. Thus, after manufacture it is necessary to inspect the blades to ensure the holes are properly positioned. Current inspection systems require inspection of each cooling hole from a gun-barrel view, which typically requires the use of a five-axis computer numerically controlled (CNC) machine for moving the probe. Due to the CNC machine, such systems are quite expensive and take up a large amount of floor space in production facilities. Also, for example, since as many as eighty holes must be individually inspected on each blade, inspection of a single blade may take as long as ten minutes. Therefore, there is a need for improved methods and systems for quickly and accurately determining the location of holes and other features on the surface of a turbine blade.